converting std::string to upper case without modifying source

Question

I'm acquainted with the usage of std::transform(data.begin(), data.end(), data.begin(), ::toupper), which can change the string in data to all uppercase. I am wondering, however, if there is a clean solution that can get the all-uppercase version of a string without modifying the source? The workaround of making a copy of the source and then calling std::transform on the copy, and then returning the copy seems a bit like a kludge, and I'm wondering if there's a more efficient and elegant solution.

I am looking for a pure C++11 solution... without dependency on any even widely available C++ libraries such as boost.

"making a copy of the source and then calling std::transform on the copy, and then returning the copy " Is as efficient as you would get if you're not changing the source. — Jagannath
– Jagannath, Commented Nov 6, 2014 at 3:03
do you mean that somehow the string is turned uppercase at compilation time, while being lowercase in the source? — didierc
– didierc, Commented Nov 6, 2014 at 6:01
std::string udata; std::transform(data.begin(), data.end(), std::back_inserter(udata), ::toupper);. Nothing says the transformation must happen in place. — Igor Tandetnik
– Igor Tandetnik, Commented Nov 6, 2014 at 6:04
If you post that comment as an answer, I will flag it as the correct answer, and the question can be marked as answered. I never knew about std::back_inserter. Most cool. Thanks. — markt1964
– markt1964, Commented Nov 6, 2014 at 21:48

markt1964 · Accepted Answer · 2014-11-10 18:58:20Z

Per Igor's comment above, the solution is to use an std::back_inserter on the destination.... std::transform(src.begin(), src.end(), std::back_inserter(dest), ::toupper);

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